Method of making tapered ground joints



`July 5, 1949- w. o. LUERTZING 2,475,431

METHOD OF MAKING TAPERED GROUND JOINTS Filed Feb. 28, 1948 1N ENTORATTORNEYS Patented July 5, 1949 METHOD F MAKING TAPERED GROUND JOINTSWalter 0. Luertzing, Vineland, N. J., assignor to Lurex ManufacturingCompany,

Vineland,

N. J., a corporation of New Jersey Application February 28, 1948, SerialNo. 12,073

11 Claims.

This invention relates to the manufacture of glassware for chemical andlike use and is concerned more particularly with a novel method offorming on a glass article a circumferential enlargement of taperingdiameter which is receivable in a tapered socket to make a sealed jointof the plug and socket type. The method of the invention may be utilizedin making articles of various kinds and may be employed to especialadvantage in the manufacture of thermometers for use in chemicalapparatus. The application of the new method in connection with theproduction of thermometers will, accordingly, be illustrated anddescribed in detail for purposes of explanation, although it will beapparent that the utility of the method is not restricted to thatspecific use.

It is now common practice to construct thermometers, which are to bemounted in an opening in the wall of a vessel forming part of chemicalapparatus, with a circumferential enlargement of plug form and having aground outer surface of tapering diameter. The vessel is then made witha socket having a ground surface or corresponding taper and, when thethermometer is seated in the socket, the ground surfaces make a tightlysealed joint. Heretofore, the enlargement on the thermometer has beenmade by heating the thermometer stem between its ends with a flame andthen slowly and carefully forcing the ends of the stem toward oneanother to force the softened glass outwardly to increase the outerdiameter of the stem. The operation is carried on along the stem, untilan enlargement of suitable diameter and length has been made, and itmust be performed with great skill and attention, in order to avoidclosure or distortion of the small passage through the stem. Because ofthe delicacy and skill required in the operation and the time consumed,the production of such thermometers is not only expensive but also mosttrying to the glass workers.

The present invention is directed to the provision of a method formaking an enlargement on a glass article, such as a thermometer, whichis relatively easy to perform, can be carried out rapidly, and is notlikely to cause injury to the article, even though performed with only amodcrate degree of skill. In the practice of the new method, a length ofglass tubing is telescoped over the article and then secured thereto atthe place, where the enlargement is desired, so that it forms anintegral part of the article. The attaching of the tube to the articleis effected by operations requiring a minimum distortion of the articleand, after the tube is in place, its outer surface can be finished bythe usual operations.

For a better understanding of the invention, reference may be made tothe accompanying drawings, in which Fig. 1 is a view in side elevationof a thermometer, the stem of which has been provided with. anenlargement of plug form by the practice of.- the new method;

Fig. 2 is a View in side elevation of a portion of' the stem of thethermometer and illustrates therst step in the practice of the method;

Figs. 3 and 4 are longitudinal sectional views; through the stem of thethermometer and illustrate subsequent successive steps in the method;

Fig. 5 is a longitudinal sectional view through the stem of thethermometer on which an enlargement has been formed by the method;

Fig. 6 is a longitudinal sectional view through the stem of thethermometer showing the enlargement in its final form;

Fig. 7 is a view similar to Fig. 3 but showing a step in a modified formof the method; and

Fig. 8 is a longitudinal sectional view of the final form of thethermometer stem and enlargement made by the method involving theoperation of Fig. '7.

The thermometer shown in Fig. 1 has the usual glass stem I U terminatingat one end in a bulb i l and formed with a capillary tube I2 leadingfrom the bulb to the other end of the stem. Between its ends, andpreferably nearer the bulb end, the stem is formed with an enlargementi3, which has an external ground surface of tapering diameter, so thatthe enlargement can be seated in a corresponding ground tapered socketto make a tight sealed joint.

In the production of the thermometer shown in Fig. l by the method ofthe invention, the stem is first heated over narrow circumferentialareas Hl, l5 spaced apart a distance corresponding to the length of theenlargement to be made. The areas are heated separately by a flame and,when the glass in an area is softened, the ends of the stem are forcedtoward one another to cause the softened glass to bulge outwardly. Smallsimilar circumferential collars Illa, IEa are thus formed and, since theexternal diameter of the collars is not substantially greater than thatof the stem, the collars can be readily made without distortion of thepassage I2.

When the collars have been completed, a length of straight glass tubingI6 of uniform diameter and wall thickness and sufliciently long to spanthe distance between the collars is slipped.

"which the interior `of'theftubing is'evacuated vand 3 over the stem andcollars. The tubing preferably has an internal diameter notsubstantially greater than the external diameter of the collars and thewall thickness of the tubing is such as to provide the necessary amountof glass to make the enlargement. When the tubing has been placed inpositiony'a flame, indica-ted'at Il, `is applied to-the'l tubing outsideone collar, forfxample, the collar Illa, and, as the tubing is heated,the stem and tubing are rotated and the glass'f the tubing softens andseals to thevoutersurface of the collar at its plane of'greatestdiameten A hose I8 is then telescoped over the stem and the endof the tubing i6 remote from-"collar"` Ma. "The hose is connected to aVacuum*flpumpllandftvith the pump operating, the flame isapplied"'to"the outer surface of the tubingc-ad-jacent-collarMa and thetubing is progressivel;7` heated toward collar Ia. As the tubingsoftens, it is collapsed against the surface ofthe stem by the vacuumfand adheres'to thestem, untilrlally thetubing :is attachedtothercutersurface of the stemfbe- Itween the .planes ofisgreat'estdiameter Iof the t collars.

The hose I3 is 4then disconnectedfrom'the and removed. Any sharpedgesa'longthe-lines of fracture may be smoothed? by means ofythe-llame. 1 "The length? of "tubing thatl has' thus'been attached tothe outside/of the stemis-substantally vof-fthe .-'rshapeof 'theenlargement i9. Thereafter, the enlargement `is finished by grindingitsouter` surface-2 to the fdesirediinal'ftaperingfdiameterlandil .fpreferably, *the `vsurface T42 I connecting the'flarge `end of the'ground-fsiirfacewith fthe outerv surface of the'stem is `givenalightflnishinggrind.

In the modi-lied? 4form ofi the-method illustrated -in Figs. Tand-B,thestemt-ofithefthermometer'is" heated as before at spacedpoints tofformcollars end of the enlargement, isffof-l somewhat greater size thancollar22. After formation'ofi the'icollars, -a lengthbf-glass-tubing-24of atslightly' .greater length than the'distance betweenthe Icollars isslipped over the stem of theltherinometer. VThe inner diameter Yof 'the'tubing is fnot subfstantially greaterthantlie-'outer diameter of' col-`will telescope overcollarfilS. eAf'tel'rthe tubingfis `in place, theflared-'e-ndfis heated-until itisoftens I andseals to the` outersurfaceof ycol-lar f23, after heated to cause'the tubing-to collapse andadhere to the surface of the stem of -thethermometer between the` planesyof" greatest-diameter' of l the collars. When thetubing-hasthusbeen7attached to the stern,` thefree endbf'the vtubing ibeyond collar 22 isbroken off and thelstemis thus formed `with an enlargement,` which canlbel-groundfJtothe Y final tapered formshownatit. The-ground surfacelies approximately Vtangent to-Ythe surfacejfof the `largecollar-ZB-and, asl-the surfacefZSf ofthe' collar is smooth, vit-doeslnot require* any-finish #grinding With the method-described,.thefstem-of the article is' subjected `to* only. 'minor -1distortion` l-to form the spaced collarsf-atfoppositeendscf-theenlargement and, in the case-cfathermometer,

lthe collars can rbe-rea'dily formed without-distor- 4tion of thecapillaryftube. Themse?oftheh'length of tubing makes the provisionV of'the Anecessary body of .glass V-to form the f plug enlargement onv an'fen'lar'genient receivable; iny a :groundsocket to make a tight joint,the steps of heating the artifcle over narrow circumferential areas tosoften it and forcing its ends together to form circum- Aferei'itialcollars at spaced points, telescoping a length of glass tubing over thearticle, the tubing extending from-'onecollar to the other, heating`$1.5'ithetubi'ng tol-soften it, and, while the tubing is being' heated,evacuating its interior to cause it to be drawn inwardly to adhere tothe article.

2. lIn a method of forming a glass article with @anenlargementreceivable in a ground socket to make a tight joint, the steps ofheating the article over l narrow ycircumferential areas to soften itan-d f forcing its endsA together toform circuml ferential collars atspaced points; telescoping: over `the-article and collars a-lengthofglass tubing Q5 eXtendingvfr-omone collar-to the othergheating thetubing adjacent one collar to cause the tubl ing' to'vadhere to thecollar-entirely -around ythe latter; evacuating the interiorof :thetubing betweenthe collars, and heating the 'tubing uprogressively fromthe collar,'to-w-hich= the tubing'is VVconnected, to the other collarto'softenthe tubing, until the vacuum within the -tubing draws it intocontact with thearticle.

-3. In -a method of forming a'glassv article with I an enlargementreceivable Yin -a ground: socket to make'a tight ljoiI-1t,vthe`A steps-ofheating the article over narrow circumferential areasto'soften itandY forcing its endsftogether to4v form circumferentiall collarsatspaced points, ,telesccping a 40 lengthA ofglass tubing over thelarticleto enclose the collars-and` the-portion ofl-the'article betweenthem, heating the' tubing at one collar untill the tubing `softens andbecomessealed t0 the surface ofthe collar,rconnectingtheend ofthe tubingadjacent-the second collar to a sourcelofvacuum, progressively heatingthe v tubing from lthefirst coll-ar -to Ythe second, -until'theYtubingcollapses against the surface 'oflthearticle andy adheresthereto, and breakingoffffree portions of "the vtubing beyondthecollars.

4. In'a-` method of forming-a glass articlewith an .enlargementreceivable in# aground socket to :make a tightjoint,l thesteps ofheating the article over -narrow circumferential areas to soften -it-and forcing itsends togethento form collars'lof approximately the sameexternal'- diameter at fspaced poin-ts-,telescopi-nga-length'of glasstubing of substantially-uniform internal diameter and Wall thicknessoverf--the articleand f collars, heatingf the tubingad-jacent one-collartocause the tion is continui-ng tubing -to adhereto :thearticleientirely' around the latter, evacuating thef-interiorof the tubing fromits connection -to -thecollarcthrough the opposite Iend `of thetubing;ar1d,-while the evacua- -progressivelyfheating'the tub- 1 ingfromits yconnection'to said vcollar to the-'other collar,` until thetubi-ng" collapsesandf adheres to the -article atand betweenthe-collars.

5.- In a methodfofforminga glass article -vwith 7o-1an enlargement4receivable lin aground socket-to make a tight-joint, the steps ofhea-tingl thefarticle i over narrow-=circum-ferential areasto'sof'tenh-it and-forcing its ends together -to form -circumferential'collars'atv-spaced points', one of the' co1- larsbeingy of ilarger-external-diameterthanthe other, telescoping a piece of glasstubing with a flared end over the article, the flared end overlying thelarge collar and the tubing extending past the small collar, heating thetubing at the liared end until the tubing adheres to the outer surfaceof the large collar, evacuating the tubing through the opposite end,and, while the evacuation is continuing, progressively heating thetubing from the large collar toward the small collar, until the tubingcollapses against the other surface of the article and adheres theretobetween and at the collars.

6. A method of forming a glass article with an enlargement receivable ina ground tapered socket to make a tight joint, which comprises heatingthe article to soften it over narrow circumferential areas and forcingits ends together to form circumferential collars at spaced points,telescoping a length of glass tubing over the article, the tubingextending from one collar to the other, evacuating the interior of thetubing, heating the tubing, while the evacuation is continuing, to causethe tubing to collapse and adhere to the article between and at thecollars, and grinding the outer surface of the tubing to a taperingdiameter.

7. A method of forming a glass article with an enlargement receivable ina ground tapered socket to make a tight joint, which comprises heatingthe article to soften it over narrow circumferential areas and forcingits ends together to form circumferential collars at spaced points,telescoping a length of glass tubing over the article, the tubingextending from one collar to the other, evacuating the interior of thetubing,

heating the tubing, while the evacuation is continuing, to cause thetubing to collapse and adhere to the article between and at the collars,cutting off `the tubing at the collars, and grinding the outer surfaceof the tubing to a tapering diameter.

8. A method of forming a glass article with an enlargement receivable ina ground tapered socket to make a tight joint, which comprises heatingthe article to soften it over narrow circumferential areas and forcingits ends together to form circumferential collars at spaced points,telescoping a length of glass tubing over the article, the tubingextending from one collar to the other, evacuating the interior of thetubing, heating the tubing, while the evacuation is continuing, to causethe tubing to collapse and adhere to the article between and at thecollars, cutting off the tubing at the collars, grinding the outersurface of the tubing to a tapering diameter, and grinding the surfaceconnecting the surface of the article with the large end of the taperedsurface.

9. A method of forming a glass article with an enlargement receivable ina ground tapered socket to make a tight joint, which comprises heatingthe article over narrow circumferential areas to soften it and forcingits ends together to form circumferential collars at spaced points,

one collar being larger than the other, flaring one end of a straightpiece of glass tubing having an internal diameter not substantiallygreater than the external diameter of the small collar, so that theflared end will receive the large collar, telescoping the piece oftubing over the article with the flared end receiving the large collarand the small collar lying within the portion of the tubing of uniformdiameter, sealing the flared end of the tube to the surface of the largecollar, evacuating the interior of the tubing, progressively heating thetubing from the seal at the large collar toward the small collar, whilethe evacuation continues, to cause the tubing to collapse and adhere tothe surface of the article and the small collar, and grinding the outersurface of the tubing to a diameter tapering toward the small collar.

10. A method of forming a glass article with an enlargement receivablein a ground tapered socket to make a tight joint, which comprisesheating the article over narrow circumferential areas to soften it andforcing its ends together to form circumferential collars at spacedpoints, one collar being larger than the other, flaring one end of astraight piece of glass tubing having an internal diameter notsubstantially greater than the external diameter of the small collar, sothat the flared end will receive the large collar, telescoping the pieceof tubing over the article with the flared end receiving the largecollar and the small collar lying within the portion of the tubing ofuniform diameter, sealing the flared end of the tube to the surface ofthe large collar, evacuating the interior of the tubing, progressivelyheating the tubing from the seal at the large collar toward the smallcollar, while the evacuation continues, to cause the tubing to collapseand adhere to the surface of the article and the small collar, cuttingoff the free end of the tubing beyond the small collar, and grinding theouter surface of the tubing to a diameter tapering toward the smallcollar.

11. In a method of forming a glass-stemmed thermometer with anenlargement of plug form receivable in a ground socket to make a tightjoint, the steps of heating the stem of the thermometer over narrowcircumferential areas to soften it and slowly forcing the ends of thestem together to form circumferential collars at spaced points withoutsubstantial distortion of the capillary tube through the stem,telescoping a length of glass tubing over the stem, the tubing extendingfrom one collar to the other, heating the tubing to soften it, whileevacuating the interior of the tubing to cause it to collapse and adhereto the surface of the stem, cutting off the tubing at the collars, andgrinding the external surface of the tubing to a diameter taperingtoward the bulb end of the thermometer.

WALTER O. LU'ERTZING.

No=references cited.

